The long term evolution (LTE) program of the 3rd Generation Partnership Project (3GPP) has been developed to provide improved spectral efficiency, reduced latency, and better utilization of radio resources for faster user experiences and enhanced applications and lower cost services. As part of these efforts, the 3GPP has introduced a concept of an in-home evolved Node-B (HeNB) for LTE networks, which can be regarded as a kind of local area evolved Node-B (eNB). Such local area eNBs correspond to physical access devices or base station devices, which may be similar to a wireless local area network (WLAN) access point (AP). The local area eNB provides users with access to LTE services over extremely small service areas, such as homes or small offices. The local area eNB is intended to connect to the operator's core network by using, for example, public Internet connections, for example, digital subscriber line (DSL). This can be useful in areas where LTE has not been deployed, and/or in areas where conventional or legacy 3GPP radio access technology coverage already exists. Furthermore, the above concept may also be useful in areas where LTE coverage may be faint or non-existent due to, for example, the occurrence of radio transmission problems, in an underground metro or shopping mall, for example.
A local area eNB may be used to deploy one or more closed subscriber group (CSG) cells which are a defined area over which radio coverage provided by the local area eNB may only be accessed by a group of subscribers authorized to use the services of the cell. The subscriber, whether an individual or an organization, may deploy a CSG cell using a local area eNB over an area where such a service is desired.
Cheap deployment of local area eNBs could be achieved, if global synchronization (achieved for example by a common clock based on the Global Positioning System (GPS)) was dispensed with and synchronization between eNBs was handled via the air interface between the eNBs. This however might lead to a problem in case one eNB is transmitting to terminal devices (for example user equipments (UEs)) while other eNBs are transmitting a synchronization signal.
When an eNB is booting in the vicinity of other eNBs in an uncoordinated deployment without global synchronization, it could start by a cell search procedure by which surrounding cells can be detected. Then, the corresponding system information could be decoded. This system information could also contain over-the-air communication (OTAC) configuration parameters, so that the eNB is enabled to start operating and also receive OTAC messages from other base stations or access devices via an air interface after synchronization is obtained.
However, eNBs which are already in operation may not yet have synchronized/detected the new eNB and could thus not be able to receive OTAC messages from the new eNB if reception of OTAC messages requires such synchronization/detection.